CN103024921B - A kind of dispatching method divided into groups based on CQI feedback parameter and SINR numerical value - Google Patents

Abstract

The invention discloses a kind of dispatching method divided into groups based on CQI feedback parameter and SINR numerical value, the SINR numerical value of all users in the calculation plot of base station; SINR threshold value is set, the user area being more than or equal to SINR threshold value is divided into Cell Center User group I, the user area being less than SINR threshold value is divided into Cell Edge User group II, and by resource block assignments total in community to Cell Center User group I and Cell Edge User group II in order to scheduling; In a time window, the user that base station is followed successively by every group according to CQI mechanism distributes corresponding Resource Block, adopts PF dispatching method and RR dispatching method to dispatch respectively to Cell Center User group I and Cell Edge User group II.By building LTE system simulation model, this algorithm and PF algorithm being carried out simulation comparison, show that this algorithm improves the fairness between the throughput of community and user to a certain extent compared with PF algorithm by simulation result.

Description

A kind of dispatching method divided into groups based on CQI feedback parameter and SINR numerical value

Technical field

The invention belongs to wireless communication technology field, particularly a kind of dispatching method divided into groups based on CQI feedback parameter and SINR numerical value.

Background technology

Dispatching algorithm based on LTE system is a core technology in its RRM (Radio ResourceManagement, RRM) technology, determines the performance of whole system.How what dispatching algorithm mainly solved is multiple user, when contention for resources, provides Resourse Distribute and multiplexing, and how to determine a kind of SO service order on the basis of packet data transmission.Mainly based on channel condition during scheduling, the situations such as the priority of the data volumes to be sent such as consideration simultaneously and business, and give full play to Adaptive Modulation and Coding (Adaptive Modulation and Coding, AMC) effect of automatic repeat request (HybridAutomatic Repeat reQuest, HARQ) and CQI feedback parameter mechanism, is mixed.Dispatching algorithm should allow the user with moment best channel condition accept service, can reach the highest user data rate and maximum throughput of system like this, but also will take into account grade and the fairness of each user simultaneously in each moment.

Packet scheduling algorithm the most frequently used in LTE system has 3 kinds: repeating query (Round Robin, RR) algorithm, max carrier to interference (Maximum Carrier to Interference, MAX C/I) algorithm and equitable proportion (Proportional Fair, PF) algorithm.

RR(Chuanxiong Guo.Improved Smoothed Round Robin Schedulers forHigh-Speed Packet Networks [A] .IEEE the27th Conference on ComputerCommunications [C], 2008:1579-1587) be a kind of for different grouping queue provide indifference dispatcher can packet scheduling algorithm, its basic thought is that the Radio Resource that sequential loop that the different user ensured in community can be determined according to certain takies equivalent communicates.Suppose to have in community and N number ofly treat dispatched users, then the definition of probability that is scheduled of each user is as follows:

$P_i\left(t\right)=\frac{1}{N},i\∈[1,N]---\left(1\right)$

In formula, N is total number of users to be scheduled in community, and i is i-th user in needed dispatched users, and its span is arbitrary integer of [1, N].The chance that arbitrary user in community is scheduled is equal.

The Knopp of Eurecom institute of France proposes a kind of packet scheduling algorithm with maximum system throughput, be referred to as MAX C/I algorithm (Knopp R, Humblet P.A.Information capacity andpower control in single-cell multiuser communications [J] .IEEE InternationalConference on ' Ggateway to Globalization ' Communications, 1995, vol.1:331-335) its basic thought is the user of all waits sorted according to the size of the carrier/interface ratio of its Received signal strength, when each scheduling, always selective channel condition is good, the user with max carrier to interference provides dispatcher meeting, its dispatching priority computing formula is as follows:

$P_i\left(t\right)=\underset{i}{\arg \max }\left\{\frac{C_i}{I_i}\right\},i\∈[1,N]---\left(2\right)$

In formula, N is total number of users to be scheduled in community, and i is i-th user in needed dispatched users, C _i/ I _iit is the carrier/interface ratio of i-th user.

The Jack M.Holtzman of Qualcomm proposes a kind of PF dispatching algorithm (Jack M.Holtzman.Cdma Forward Link Waterfilling Power Control [J] .IEEE51st VehicularTechnology Conference Proceedings, Tokyo, 2000, vol.3:1663-1667), its basic thought is the fairness simultaneously taken into account between the throughput of system and user, treat that for community is each dispatched users distributes a corresponding with it priority, each time slot scheduling has the user of limit priority to provide service, its dispatching priority computing formula is as follows:

$P_i\left(t\right)=\underset{i}{\arg \max }\left\{\frac{\mathrm{DR}{C}_i\left(t\right)}{{\stackrel{\‾}{R}}_i\left(t\right)}\right\},i\∈[1,N]---\left(3\right)$

In formula, DRC _it () is the peak transfer rate that i-th user can reach when t; for the average transmission rate of this user before moment t, its update rule is shown below:

$\stackrel{\‾}{R_i\left(t\right)}=(1-\frac{1}{t_c})\·\stackrel{\‾}{R_i(t-1)}+\frac{1}{t_c}\·{\mathrm{DRC}}_i(t-1)---\left(4\right)$

In formula, t _cfor window update time, its length has strict requirement usually, generally will be enough to the change covering rapid fading, and meet the delay requirement of user.

Be not difficult to find out from above-mentioned three kinds of classical dispatching algorithms, RR algorithm is considered to a kind of algorithm the most fair, but due to Round Robin and the otherness reckoned without in wireless channel conditions residing for the QoS demand of each different user business in community and user, therefore the resource utilization of this algorithm is not high, and throughput of system is lower.

MAX C/I algorithm can obtain higher throughput, the availability of frequency spectrum is higher, but for the user near apart from base station because its channel condition can receive service well always, and the user being in cell edge due to C/I lower, these users will can not get service opportunity, even there will be " phenomenon hungry to death ", therefore this algorithm is the most inequitable.

PF is based on the fair dispatching algorithm of part, has done a compromise between fairness and integrated scheduling efficiency.PF is not the most fair, and efficiency neither be the highest, but it is the algorithm of fair relatively and relative efficiency, and its major defect is the requirement of service quality (Quality of Service, QoS) requirement, particularly time delay not considering different business.

And if the lifting of throughput and fairness can be realized simultaneously, will be highly significant.

Summary of the invention

The problem that the present invention solves is to provide a kind of dispatching method divided into groups based on CQI feedback parameter and SINR numerical value, overcomes the problem of not easily compromising between cell throughout and fairness, improves the fairness between the throughput of community and user to a certain extent.

The present invention is achieved through the following technical solutions:

Based on the dispatching method that CQI feedback parameter and SINR numerical value are divided into groups, comprise the following steps:

1) the SINR numerical value of all users in the calculation plot of base station;

2) SINR threshold value is set, the user area being more than or equal to SINR threshold value is divided into Cell Center User group I, the user area being less than SINR threshold value is divided into Cell Edge User group II, and number of resource blocks total in community is distributed to Cell Center User group I and Cell Edge User group II in order to scheduling;

3) in a time window, the user that base station is followed successively by every group according to CQI mechanism distributes corresponding Resource Block, adopts PF dispatching method and RR dispatching method to dispatch respectively to Cell Center User group I and Cell Edge User group II;

4), after next time window starts, base station calculates its respective SINR numerical value, according to step 1) ~ 3 again to current residual user in community) carry out dispatching until intra-cell users finishing scheduling.

The method of the SINR numerical value of described calculating user is:

For any time t, arbitrary cells n, calculates the distance L of active user i distance base station respectively _i, antenna gain A _iand neighbor cell is to the interference I of this user _i, then the SINR numerical value of user i is determined by following formula:

${\mathrm{SINR}}_i=\frac{P_{\mathrm{TX}}-L_i-A_i}{\mathrm{Noise}+I_i}$

Wherein P _tXfor the base station transmitting power of current area, Nosie is system thermal noise.

Described SINR threshold value is the mean value of the user participating in SINR numerical computations in current time window.

The ratio of the Resource Block that described Cell Center User group I and Cell Edge User group II are distributed is 8:2 ~ 9:1.

The user that base station is followed successively by every group according to CQI mechanism distributes corresponding Resource Block, and the SINR value of each user obtains the CQI numerical value of its correspondence by following formula:

CQI _i=fix(0.35*SINR _i+1)+1,SINR _i∈[-2,42]；

And then with reference to the mapping relations of CQI and MCS and number of resource blocks, the modulation system obtaining taking in scheduling process for this user, code rate, code efficiency are to advise the resource block number of distribution.

Being scheduling to Cell Center User group I in described step 3):

To the user in Cell Center User group I, be followed successively by user according to CQI mechanism and distribute corresponding Resource Block, dispatch according to PF dispatching algorithm, its dispatching priority is defined as follows:

$P_i\left(t\right)=\frac{{\mathrm{DRC}}_i\left(t\right)}{\stackrel{\‾}{R_i\left(t\right)}}$

In formula, DRC _it () refers to the maximum rate that i-th user can reach in t; And refer to the average transmission rate of this user before t, renewal meet following rule:

$\stackrel{\‾}{R_i\left(t\right)}=(1-\frac{1}{t_c})\·\stackrel{\‾}{R_i(t-1)}+\frac{1}{t_c}\·{\mathrm{DRC}}_i(t-1)$

In formula, t _cfor window update time.

Being scheduling to of described step 3) small area edge customer group II:

To the user in Cell Edge User group II, be followed successively by user according to CQI mechanism and distribute corresponding Resource Block, dispatch according to RR dispatching algorithm, the dispatching priority of each user is all identical, N number ofly treat dispatched users if having in this group, then the probability that is scheduled of each user is as follows:

$P_i\left(t\right)=\frac{1}{N},i\∈[1,N]$

In formula, N is total number of users to be scheduled in group, and i is i-th user treated in dispatched users, and its span is arbitrary integer of [1, N].

Compared with prior art, the present invention has following useful technique effect:

The dispatching method divided into groups based on CQI feedback parameter and SINR numerical value provided by the invention, based on LTE system, by calculate each user SINR numerical value, reasonably grouping SINR threshold value is set, user is divided into Cell Center User group I and Cell Edge User group II, be convenient to the reasonable distribution of scheduling resource block, Cell Center User group I can distribute relatively many Resource Block in order to scheduling, improves throughput of system; And Cell Edge User distributes relatively less Resource Block group II, to prevent " dying of hunger " phenomenon;

Be that each user distributes corresponding scheduling resource block and determines corresponding MCS in conjunction with CQI feedback parameter simultaneously, because CQI feedback parameter is the data rate supported by channel, and consider the SINR of user and the feature of receiver, so just comparatively can choose corresponding modulation system, code rate, code efficiency and resource block number for each user easily, thus reduce the signaling consumption of system, be conducive to the fairness between the throughput of raising system and user;

Then different dispatching algorithms is used to implement scheduling to the user in each grouping, because Cell Center User has channel condition relatively preferably, adopt PF algorithm to implement scheduling to user in group I and can improve throughput of system, also can take into account the fairness of user simultaneously; User due to cell edge has relatively poor channel condition, adopts RR algorithm to implement to dispatch the long-term fairness that can ensure between user to user in II, and realizes comparatively simple.

By building LTE system simulation model, the dispatching method divided into groups based on CQI feedback parameter and SINR numerical value provided by the invention, carry out simulation comparison with PF algorithm, show that this algorithm improves the fairness between the throughput of community and user to a certain extent compared with PF algorithm by simulation result.

Accompanying drawing explanation

Fig. 1 is main modular relation schematic diagram;

Fig. 2 is user movement model schematic;

Fig. 3 is PF algorithm Resourse Distribute schematic diagram;

Fig. 4 is RR algorithm Resourse Distribute schematic diagram;

Fig. 5 is SINR and CQI corresponding relation figure;

Fig. 6 is throughput window t in time _cat the comparison diagram of innovatory algorithm and PF algorithm;

Fig. 7 is the fairness window t in time between user _cat the comparison diagram of innovatory algorithm and PF algorithm.

Embodiment

Below in conjunction with specific embodiment, the present invention is described in further detail, and the explanation of the invention is not limited.

Based on the dispatching method that CQI feedback parameter and SINR numerical value are divided into groups, comprise the following steps:

1) the SINR numerical value of all users in the calculation plot of base station;

2) SINR threshold value is set, the user area being more than or equal to SINR threshold value is divided into Cell Center User group I, the user area being less than SINR threshold value is divided into Cell Edge User group II, and number of resource blocks total in community is distributed to Cell Center User group I and Cell Edge User group II in order to scheduling;

3) in a time window, the user that base station is followed successively by every group according to CQI mechanism distributes corresponding Resource Block, adopts PF dispatching method and RR dispatching method to dispatch respectively to Cell Center User group I and Cell Edge User group II;

4), after next time window starts, base station calculates its respective SINR numerical value, according to step 1) ~ 3 again to current residual user in community) carry out dispatching until intra-cell users finishing scheduling.

Below from carry out the model dispatched and concrete operating procedure is described.

First the system model that the dispatching method based on CQI feedback parameter and the grouping of SINR numerical value is described is provided.

1, constructing system model (see Fig. 1, Fig. 2)

(1) cellular cell model

The network topology structure that native system adopts is three layers of 19 cellular cell model, and each radius of society is 500m, and base station is positioned at the center of community, and each community is divided into three sectors by directional antenna, and each community can be subject to the interference from other 18 communities.

(2) user movement model

Distance between user and base station must not be less than 35 meters, and radius of society is R, and the coordinate of user is (x, y), and movement angle is angle, and rate travel is V, and the location updating time is TTI, then the coordinate distribution of arbitrary user is x ∈ [-R, R], its location updating formula is:

x _i(t)=x _i(t-1)+V·TTI·cos(angle) （5）

y _i(t)=y _i(t-1)+V·TTI·cos(angle) （6）

(3) channel model

In native system, hypothesis is the communication environment in urban district or the suburbs, and path loss formula is:

L _i=40(1-40×10 ^-3·H _b)·lg(d _i)-18·lg(H _b)+21·lg(f _c)+80(dB) （7）

In formula, H _brepresent the height of antenna for base station relative to average top of building, d is expressed as the distance of user to base station, f _cfor the centre frequency of carrier wave.

Antenna gain computing formula is:

In formula, wherein, θ is defined as the angle of link and antenna boresight direction, θ _3dB3dB wave beam bandwidth, A _mit is maximum attenuation amount.

System adopt be three layer of 19 beehive area structure and frequency duplex factor as one is 1, so the interference that the subcarrier that each subcarrier can be subject to the same frequency coming from all the other 18 communities brings.

What Installed System Memory then adopted at noise is thermal noise, and its frequency spectrum is-174dBm/Hz.

(4) business model

Adopt a kind of comparatively simple but very practical FullBuffer model, namely base station side can send data in the moment, and user side also can keep one's powder dry reception data.

2, the SINR numerical value of all users in calculation plot

For any time t, arbitrary cells n, calculates the distance L of active user i distance base station respectively _i, antenna gain A _iand neighbor cell is to the interference I of this user _i, then the SINR numerical value of user i is determined by following formula:

${\mathrm{SINR}}_i=\frac{P_{\mathrm{TX}}-L_i-A_i}{\mathrm{Noise}+I_i}$

P in formula _tXfor base station transmitting power, its value is 43dBm; Nosie is system thermal noise, and its power spectral density is-174dBm/Hz.

3, the mean value arranging the user participating in SINR numerical computations in current time window is SINR threshold value in order to divide into channel quality good Cell Center User group I and the poor Cell Edge User group II of channel quality, and joins different Resource Block in order to scheduling to two components.

(1) division rule of class of subscriber

When user i meets SINR _i>=SINR _thrtime, be judged to be Cell Center User, be divided into group I; When user i meets SINR _i<SINR _thrtime, be judged to be Cell Edge User, be divided into group II, SINR _thrfor SINR threshold value, be specially the mean value of the user participating in SINR numerical computations in current time window.

(2) division rule of Resource Block

Suppose that the Resource Block total number that can for call in current area is N _rB=100, then distribute 90% × N to group I _rB=90 Resource Block are in order to scheduling; 10% × N is distributed to group II _rB=10 Resource Block are in order to scheduling.

4, respectively group I and group II adoption rate fair algorithm (PF) and Round-Robin Algorithm (RR) are dispatched.

(1) see Fig. 3, to the user in group I, be followed successively by user according to CQI mechanism and distribute corresponding Resource Block, dispatch according to PF dispatching algorithm, its dispatching priority is defined as follows:

$P_i\left(t\right)=\frac{{\mathrm{DRC}}_i\left(t\right)}{\stackrel{\&OverBar;}{R_i\left(t\right)}}$

In formula, DRC _it () refers to the maximum rate that i-th user can reach in t; And refer to the average transmission rate of this user before moment t, its renewal meets following rule:

$\stackrel{\&OverBar;}{R_i\left(t\right)}=(1-\frac{1}{t_c})\&CenterDot;\stackrel{\&OverBar;}{R_i(t-1)}+\frac{1}{t_c}\&CenterDot;{\mathrm{DRC}}_i(t-1)$

In formula, t _cfor window update time, its length has strict requirement usually, generally will be enough to the change covering rapid fading, and meet the delay requirement of user.

(2) see Fig. 4, to the user in group II, be followed successively by user according to CQI mechanism and distribute corresponding Resource Block, dispatch according to RR dispatching algorithm, the dispatching priority of each user is all identical, and its definition of probability be scheduled is as follows:

$P_i\left(t\right)=\frac{1}{N},i\&Element;[1,N]$

In formula, N is total number of users to be scheduled in group, and i refers in particular to i-th user in needed dispatched users, and its span is arbitrary integer of [1, N].From above formula, the chance that the arbitrary user in community is scheduled is equal.

(3) the CQI mechanism described in is based on a set of Block Error Rate (Block Error Rate, BLER), and user modulates and encoding scheme (Modulation andCoding Scheme, MCS) report CQI values according to corresponding based on the received signal quality measured.

CQI _i=fix(0.35*SINR _i+1)+1,SINR _i∈[-2,42] （9）

Concrete Fig. 5 is SINR and CQI corresponding relation figure, and table 1 is the mapping relations table of CQI and MCS and number of resource blocks,

The mapping relations table of table 1CQI and MCS and number of resource blocks

CQI marks	Modulation	Code rate	Code efficiency	The resource block number that suggestion distributes
					1	Without transmission	-	-	0
2	QPSK	78	0.1523	1
					3	QPSK	120	0.2344	5
4	QPSK	193	0.3770	10
					5	QPSK	308	0.6016	15
6	QPSK	449	0.8770	16
					7	QPSK	602	1.1758	20
8	16QAM	378	1.4766	35

9	16QAM	490	1.9141	35
					10	16QAM	616	2.4063	40
11	64QAM	466	2.7305	75
					12	64QAM	567	3.3223	75
13	64QAM	666	3.9023	75
					14	64QAM	772	4.5234	85
15	64QAM	873	5.1152	95
					16	64QAM	948	5.5547	100

The CQI numerical value of its correspondence can be obtained by the SINR value of each user by above-mentioned formula (9), refer again to the scheduling process of modulation system table 1 can obtain should taking in to(for) this user, code rate, code efficiency to advise the resource block number distributed.

5, after next time window starts, its respective SINR numerical value is recalculated to remaining users in current area, and is reclassified as two groups, take above-mentioned two kinds of dispatching algorithms respectively, until finishing scheduling.

Build LTE system simulation model according to the system emulation optimum configurations table shown in table 2, dispatching method of the present invention and PF dispatching method are contrasted.

Result is as shown in Fig. 6, table 3, table 4, Fig. 7, and result shows that dispatching method of the present invention and PF dispatching method improve the fairness between the throughput of community and user to a certain extent.

Table 2 system emulation optimum configurations table

Parameter	Numerical value
		Total number of users (UE)	500
Resource Block (RB) sum	100
		Resource Block (RB) size	12 subcarriers
User resource allocation block number (N PRB）	Table 1
		Base station transmitting power (P TX）	43dBm

Base station height (H b）	50m
		Thermal noise power (Noise)	-174dBm/Hz
User moving speed (V)	3km/h
		Transmission Time Interval (TTI)	0.001s
Simulation time (T)	1000*TTI
		Time window parameter (t C）	1000
Modulation system (MCS)	QPSK、16QAM、64QAM
		Code check	Table 1
Centre frequency (f C）	2000MHz

Table 3 the present invention and PF algorithmic system throughput contrast table

Fairness contrast table between table 4 the present invention and PF algorithm user

Claims (4)

1., based on the dispatching method that CQI feedback parameter and SINR numerical value are divided into groups, it is characterized in that, comprise the following steps:

1) the SINR numerical value of all users in the calculation plot of base station;

2) SINR threshold value is set, the user area being more than or equal to SINR threshold value is divided into Cell Center User group I, the user area being less than SINR threshold value is divided into Cell Edge User group II, and number of resource blocks total in community is distributed to Cell Center User group I and Cell Edge User group II in order to scheduling;

3) in a time window, the user that base station is followed successively by every group according to CQI mechanism distributes corresponding Resource Block, adopts PF dispatching method and RR dispatching method to dispatch respectively to Cell Center User group I and Cell Edge User group II;

4), after next time window starts, base station calculates its respective SINR numerical value, according to step 1 again to current residual user in community) ~ 3) carry out dispatching until intra-cell users finishing scheduling;

The method of the SINR numerical value of described calculating user is:

For any time t, arbitrary cells n, calculates the distance L of active user i distance base station respectively _i, antenna gain A _iand neighbor cell is to the interference I of this user _i, then the SINR numerical value of user i is determined by following formula:

${\mathrm{SINR}}_i=\frac{P_{\mathrm{TX}}-L_i-A_i}{\mathrm{Noise}+I_i}$

Wherein P _tXfor the base station transmitting power of current area, Nosie is system thermal noise;

Described SINR threshold value is the mean value of the user participating in SINR numerical computations in current time window;

Described step 3) in being scheduling to Cell Center User group I:

To the user in Cell Center User group I, be followed successively by user according to CQI mechanism and distribute corresponding Resource Block, dispatch according to PF dispatching algorithm, its dispatching priority is defined as follows:

$P_i\left(t\right)=\frac{{\mathrm{DRC}}_i\left(t\right)}{\stackrel{\&OverBar;}{R_i\left(t\right)}}$

In formula, DRCi (t) refers to the maximum rate that i-th user can reach in t; And refer to the average transmission rate of this user before t, renewal meet following rule:

$\stackrel{\&OverBar;}{R_i\left(t\right)}=(1-\frac{1}{t_c})\&CenterDot;\stackrel{\&OverBar;}{R_i(t-1)}+\frac{1}{t_c}\&CenterDot;{\mathrm{DRC}}_i(t-1)$

In formula, t _cfor window update time.

2., as claimed in claim 1 based on the dispatching method that CQI feedback parameter and SINR numerical value are divided into groups, it is characterized in that, the ratio of the Resource Block that described Cell Center User group I and Cell Edge User group II distributes is 8: 2 ~ 9: 1.

3. as claimed in claim 1 based on the dispatching method that CQI feedback parameter and SINR numerical value are divided into groups, it is characterized in that, the user that base station is followed successively by every group according to CQI mechanism distributes corresponding Resource Block, and the SINR value of each user obtains the CQI numerical value of its correspondence by following formula:

CQI _i＝fix(0.35*SINR _i+1)+1，SINR _i∈[-2，42]；

And then with reference to the mapping relations of CQI and MCS and number of resource blocks, the modulation system obtaining taking in scheduling process for this user, code rate, code efficiency are to advise the resource block number of distribution.

4., as claimed in claim 1 based on the dispatching method of CQI feedback parameter and the grouping of SINR numerical value, it is characterized in that, described step 3) being scheduling to of small area edge customer group II:

To the user in Cell Edge User group II, be followed successively by user according to CQI mechanism and distribute corresponding Resource Block, dispatch according to RR dispatching algorithm, the dispatching priority of each user is all identical, N number ofly treat dispatched users if having in this group, then the probability that is scheduled of each user is as follows:

$P_i\left(t\right)=\frac{1}{N},i\&Element;[1,N]$

In formula, N is total number of users to be scheduled in group, and i is i-th user treated in dispatched users, and its span is arbitrary integer of [1, N].